A thermal print head is a device for printing images or characters by locally heating a printing object such as thermal paper (see Patent Document 1, for example). FIG. 4 shows an example of a conventional thermal print head. In the illustrated thermal print head X, an electrode 93 is disposed on a substrate 91 formed with a partial glaze 92, and part of the electrode extends in the secondary scanning direction. A heat-generating resistor 94, crossing the electrode 93, is formed to extend in the primary scanning direction. The heat generating resistor 94 is covered by a protective layer 95. Current is applied to the heat generating resistor 94 via the electrode 93 while the thermal paper, pressed onto the protective layer 95, is moved in the secondary scanning direction. The current application causes the heat generating resistor 94 to generate heat, whereby desired images and characters can be printed on the thermal paper.
A drawback to printing using the thermal print head X is the sticking phenomenon, in which the thermal paper sticks to the protective layer 95. Such sticking may occur intermittently, thereby causing part of a printed character to be unduly elongated in the primary scanning direction.
Patent Document 1: JP-A-2002-2005